1. Field
The present invention concerns wireless communications, and more specifically, to methods and apparatuses for transmitting a reference signal in a wireless communication is system.
2. Discussion of the Background
Multi-cell cooperation has been introduced to raise performance and communication capacity of a wireless communication system. The multi-cell cooperation is also called cooperative multiple-point transmission and reception (CoMP).
Examples of CoMP include a beam avoiding scheme that mitigates interference to a user that is positioned at a cell boundary by cooperation of adjacent cells and a joint transmission scheme that transmits the same data by cooperation of adjacent cells.
A major requirement for next-generation wireless communication systems is to enhance capabilities for users that experience severe interference from an adjacent cell at a cell boundary, and in response to such requirement, CoMP may be put in consideration.
Various scenarios may be involved in such CoMP environment.
There are an intra-site CoMP environment (first scenario) where multiple cells are positioned around one base station, a high-power RRH CoMP environment (second scenario) where a plurality of high-power remote radio heads (RRHs) are positioned around one macro cell, and a low-power RRH CoMP environment where a low-power RRH is positioned around one macro cell, which includes two cases: one where the cell ID of the RRH is the same as the cell ID of the macro cell, and the other where the cell ID of the RRH is different from the cell ID of the macro cell (the latter case is third scenario, and the former case is fourth scenario).
Among such CoMP environments, in case a specific cell such as macro cell has a different cell ID from the cell IDs of RRHs constituting a CoMP set, differences between reference signal sequences that are based on their respective cell IDs may cause collisions. Therefore, a need exists for a method of addressing such collisions.